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456                   &YAENODON  AND   PATjRlOFELlS                  CHAP.
long, and the top has a great sagittal crest. The paroccipital
processes are short and are closely applied to the inastoid processes.
The mesethmoid is larger than in the carnivorous Marsupials, and
the frontals are very large. The palate has a peculiar structure ;
in most species the hinder ends of the palatines are separated
by a narrow fissure which broadens gradually, thus forming the
posterior nares. In H. leptocephalus the posterior nares are brought
very far back by the meeting of the alisphenoids. The pre-
s-phenoid, contrary to what we find in the Dog, for example, is
chiefly concealed by the vomer, which covers it. The mandible
has a long and strong symphysis, and its angle is not inflected.
The fore-limb is described as being " weak when compared with the
modern Carnivora." The scaphoid and lunar are separate, and
there is a eentrale. The teeth present us with nearly the typical
formula. There is only one molar missing in the upper jaw. The
canines are enlarged. It has been suggested from a consideration
of its palate that Hyaenodon was a semiaquatic animal; the
deep cleaving at the extremities of the phalanges seems to point
in the same direction, since they resemble in this the genus
Patrio/elis, which there are other reasons to regard as aquatic.
This latter genus has a fore-limb which is very like that of the
Pinnipedia, the digits are much spread out, and would seem
to have supported a kind of paddle. In any case it certainly
fed upon aquatic tortoises, for their remains have been found in
its coprolites. The name Limnofelis, also applied to what appear
to have been members of this genus, is suggestive of their habits.
Patriofelis, at least one species, seems to have been of about the
size of a Lion.
Mesonyx has a brain case which is actually smaller than that
of the Marsupial FhylacimLs. The lachrymal bone is very large,
and extends a little way over the face, as is also the case with
jETyaenodon; this condition is also found in Insectivora and in
Thylacinus* The axis vertebra has a curiously-shaped spine,
which is very different from the hatchet-shaped process of that
vertebra usual in. the Carnivora, but is not unlike what exists
in the Arctoid genera Meles and Mydaus. The limbs show
. much disparity in length, and seem to argue a much-arched
back when the creature progressed. The carpus is stated to
be strikingly like that of the Insectivora. There is as in
other Ckeodottts a separation between the scaphoid and lunar;